Color improvement of drying oils



United States Patent 343L038 IMPRGVEMENT OFDRYING GHJS Robert E. Blank, Mayfield Heights, and Albert A. Artcrs, Cleveland, Ohio, assignors to The. Sherwin-Wiiiiams Company, Cieveland, Ohio, a corporation of Ohio No Drawing. Application JuneZl, 1952, Serial No. 294,924

8 Claims. (31. 260-424) This invention relates as indicated to a new and improved process for producing bleached vegetable oils of the class consisting of drying and semi-drying oils.

More specifically, this invention relates to the process of bleaching raw or degummed soya bean oil by means of heat and acylating agents in the. presence of an inert atmosphere.

There has always existed the need for a process by which raw or degummed drying and semi-drying oils such as soya bean oil could be bleached and treated to give a product that could be substituted for the more highly refined oils, such as alkali refined soya bean oil. Obviously there would be an economic gain in such substitution. The main disadvantage to theprevious use of degummed soya bean oil. in making soya' al-kyds, blown oil plasticizers and various-coating compositions has-been that of color because degurnmed soya bean oil is usually of darker color than can be used for such mentioned purposes. It is well known to those skilled in the art that heating alone will temporarily bleach, many drying or semi-drying oils. However, thisv gain in color desirability is soon lost as the heat treated oil is used as a base for other products.

Therefore, it is a principal object of this invention to provide a process whereby cheap, raw or degummed drying or semi-drying vegetable oils may be treated toreplace the more expensive refined oils;

Another object of this invention is to bleachdegummed soya bean oil so that it has substantially all of the favorable physical characteristics or constants of the refined oil, such as color, viscosity; density, and refractive indeX.

Still another object of this, invention is to economically provide a degurnmed soya bean oil of color equal to or better than alkali refined oil and the color benefit being retained in subsequent use of the product so formed.

Other objects of this invention appear asthe description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the appended claims, the following description setting forth in detail certain illustrative embodiments of the invention, such disclosed means constituting however, but a few of the various forms in which the principle of this'invention may be employed.

Broadly stated then, this invention involves a process for producing a color stable, bleached vegetable oil which comprises heating under an inert atmosphere a vegetable oil selected from the group consisting of drying and semi-drying oils with an acylating agent selected item the group consisting of acid halides and acid anhydrides of saturated or unsaturated aliphatic monocarboxylic acids containing from 2. to 18- carbon atoms in the acyl radicle at a temperature of at least about 100" C. for a period of time suflicient to substantially permanently bleach said. oil.

In the practical operation of this invention, raw or degummed soya bean oil is heated with an acylating agent in an inert atmosphere. As stated before, heat alone has been known to bleach oils of this type but it has been found that the addition of small amounts of an acylating agent such as acetic anhydride applied to the oil in an inert atmosphere gives a bleached product that maintains its light color when used for various purposes.

This process has been applied to oils other than soya bean oil such as menhaden, linseed, perilla, safilower, etc, and, although the process: is operative with respect to these oils, a preferred application of the invention is in the treatment of soya bean oil since. the improvements obtained with respectto soya bean-oil are of much greater magnitude.

In order to better illustrate this invention, examples will now be given but it is to be noted that the examples are given for purposes of illustration only and this invention is not to be limited to the scope thereof.

EXAMPLE I A 500 gram sample of. degummed soya bean oil, Gardner-Holdt (GH) color 11, n- -1-.4738, acid No. 0.6, was heated under a flow of nitrogen (0.05 cu. ft./ min.) with 2.5 gram (0.5%) acetic anhydride to 270 C. in one-half hour. The oil wasbleached to a color of 4; n 1.4740; acid No. 0.7 A similarly treated oil without added acetic anhydride had a color of 6 and substantially the same refractive index and acid number.

The use of higher concentrations of acetic anhydride, for example from 1 to 5%, does not increase the action of bleaching. In some cases higher concentrations of the anhydride caused a break or the formation of insoluble matter.

The above process was repeated on degummed soya bean oil with various other acylating agents. The results are shown in Table I.

Table I.-Efiect 0 various acylating agents Color (G-H) Agent 01 Bleached Oil None 6 0.5% butyric anhydride 4 0.5% acetyl chloride.. 4 0.5% acetic-oleic anhydn 4 0.5% acetic acid 6 It is to be noted that aceticacid does not effect bleaching while the more active acylating agents, in the form of anhydrides and acid halides do.. I

EXAMPLE 11 Heating 500 grams of degummed soya bean oil with 0.5% acetic anhydride from room temperature to 300 C. in 0.5 hour under nitrogen gave an oil color of 3. A similarly treated oil without the addition of acetic anhydride had a color of 6.

EXAMPLE III 3 EXAMPLE IV Heating 500 gm. of degummed soya bean oil with 0.5% of acetic anhydride a t-100 under nitrogen for 21 hours gave a color of 4. This oil similarly heated without acetic anhydride gave a color of 6.

EXAMPLE v Heating 3000 grams of the oil with 15 grams (0.5%) of acetic anhydride'under nitrogen to 270 C. in two hours and holding at 270 for one hour. gave an oil with a color of 3. This oil was used to make a pentaerythritol-type alkyd resinand this was compared with a similar resin made with alkali refined soya bean oil. The alkyds had similar drying characteristics. A comparison of the other properties of the alkyds is given in Table II.

Table lI.-A comparison of PE-soya alkyd resins (50% NVM in mineral spirits) From From Bleached Alkali Degummed Refined Soya Bean Soya Bean Oil Oil Viscosity (Gardner-Holdt) X W Color (Gardner-Holdt) 6-7 9 Acid Number 15. 8 17 Cure seconds 15-16 16-17 It is to be noted that the bleached soya bean oil alkyd O resin was actually lighter in color than the alkyd resin formed from the alkali refined oil.

Table IIl.Alcholysis of soya bean oils Color of Soya Bean Oil Bleached Product G-H Scale No 7-8 No 12-13 By heat alone at 235, 1.5 hr-- 8-9 By 0.5% acetic anhydride at 7 .Here again, the bleached oil product had a color rating comparable to the product obtained from the more expensive refined oils.

EXAMPLE VII The color retention of the treated oil in alkyd resins is shown again in Table IV in which are listed the resalts of the preparation of a long oil alkyd from 500 grams (0.565 mol) samples of soya bean oils, 96 grams (0.705 mol) of pentaetrythritol and 210 g. (1.4 mol) of phthalic anhydride with 0.94 ml. of lead naphthenate solution (24% lead in mineral spirits) as a catalyst. will be seen that a bleached degummed soya bean oil, made according to this process, gave a product equivalent to that of alkali refined soya bean oil.

Table I V.-Alkyds from soya bean oils Soya Bean Oil Bleached Color (1) Alkali refined No--. 9 (2) Domwnmod N0 (3) Degummed Byhe'at alone at 232 for 1 hr---- 10 (4) Degummed Bgs (ifficetlc anhydride at V 9 The vegetable oils that are treated in the manner taught by this invention are those of the group consisting of drying and semi-drying. oils, such as linseed, dehydrated castor oil, tung, oiticica, soya bean, perilla, cottonseed, safllower, chia, etc.

The acylating agents referred to in the description of this invention are those belonging in the class consisting of acid halides and acid anhydrides of saturated or unsaturated aliphatic monocarboxylic acids containing from 2 to 18 carbon atoms in the acyl radicle, such as acetyl chloride, propionyl bromide, butyryl chloride, acetyl fluoride, acetyl iodide, acetic anhydride, propionic anhydride, butyric anhydride, acetic-oleic anhydride, oleic anhydride, etc. The quantity of the acylating agent that can be used is in the range of 0.5 to 5% by weight with respect to the oil. For most purposes, from 0.5 to 1% has been found satisfactory.

V The temperature range at which the reaction may be conducted has been found to be between C. and 325 C. This is a general range found to be necessary when dealing with the various vegetable oils. However, as a practical matter, the temperatures at which the preferred embodiment of this invention best operates has been found to be approximately 250 to 300 C.

Each oil of the class to be treated, requires a different period of time to acquire the substantially permanent bleach, but in general satisfactory results are obtained when the reaction is permitted to continue for a period of 0.25 to 20 hours. The period of time required is, however, not only a function of the properties of the oil to be treated but also of the reaction temperature.

Other modes of applying the principle of this invention may be employed instead of those specifically set forth above, changes being made as'regards the details herein disclosed, provided the elements set forth in any of the following claims, or the equivalent of such be employed.

We, therefore, particularly point out and distinctly claim as our invention:

1. A process for producing a color stable, bleached vegetable oil which comprises heating under an inert atmosphere a vegetable oil selected from the group consisting of drying and semi-drying oils with an acylating agent selected from the group consisting of acid halides and acid anhydrides of aliphatic monocarboxylic acids containing from 2 to 18 carbon atoms in the acyl radicle at a temperature of from about 100 C. to about 325 C. for a period of from about 0.25 hour to about 20 hours.

2. A process for producing a color stable bleached vegetable oil which comprises heating under an inert atmosphere a vegetable ,oil selected from the group consisting of drying and semi-drying oils with 0.1 to 5.0% of an acylating agent selected from the group consisting of acid halides and acid anhydrides of aliphatic monocarboxylic acids containing from 2 to 18 carbon atoms in the acyl radicle at 100 C. to 325 C. for a period of from about 0.25 hour to about 20 hours.

3. A process forv producing a color stable bleached vegetable oil which comprises heating under an inert atmosphere a vegetable oil selected from the group consisting of drying and semidrying oils with 0.1 to 5.0% of an acylating agent selected from the group consisting of acid halides and acid anhydrides of aliphatic monocarboxylic acids containing from 2 to 18 carbon atoms in the acyl radicle at 100 C. to 325 C. for a period of time of approximately 0.25 to 20 hours.

4. A process for producing a color stable bleached vegetable oil which comprises heating under an inert atmosphere of nitrogen a vegetable. oil selected from the group consisting of drying and semi-drying oils with 0.1 to 5.0% of an acylating agent selected from the group consisting of acid halides and acid anhydrides of aliphatic monocarboxylic acids containing from 2 to 18 carbon atomsin the acyl radicle at 100 C. to 325 C for 0.25 to 20 hours.

5. A process for producing a color stable bleached vegetable oil which comprises heating under an inert atmosphere of nitrogen a vegetable oil selected from the group consisting of drying and semi-drying oils with 0.5% of acetic anhydride at 250 C. to 300 C. for 0.5 hour.

6. A process for producing a color stable bleached vegetable oil which comprises heating under an inert atmosphere a vegetable oil selected from the group consisting of drying and semi-drying oils with 0.5% of acetic anhydride at 200 C. to 300 C for 0.5 hour.

7. A process for producing a color stable bleached degummed soya bean oil which comprises heating under an inert atmosphere said degummed soya bean oil with an acylating agent selected from the group consisting of acid halides and acid anhydrides of aliphatic monocarboxylic acids containing from 2 to 18 carbon atoms in the acyl radical at a temperature of from about 100 C. to

References Cited in the file of this patent UNITED STATES PATENTS 1,986,787 Barrett Ian. 8, 1935 2,212,385 Brod Aug. 20, 1940 2,259,968 Anderson Oct. 21, 1941 2,269,243 Baxter et a1. Jan. 6, 1942 2,510,379 Christensen June 6, 1950 2,567,404 Ross Sept. 11, 1951 

1. A PROCESS FOR PRODUCING A COLOR STABLE, BLEACHED VEGETABLE OIL WHICH COMPRISES HEATING UNDER AN INERT ATMOSPHERE A VEGETABLE OIL SELECTED FROM THE GROUP CONSISTING OF DRYING AND SEMI-DRYING OILS WITH AN ACYLATING AGENT SELECTED FROM THE GROUP CONSISTING OF ACID HALIDES AND ACID ANHYDRIDES OF ALIPHATIC MONOCARBOXYLIC ACIDS CONTANING FROM 2 TO 18 CARBON ATONS IN THE ACYL RADICLE AT A TEMPERATURE OF FROM ABOUT 100* C. TO ABOUT 325* C. FOR A PERIOD OF FROM ABOUT 0.25 HOUR TO ABOUT 20 HOURS. 